TTL computing

From: Richard Erlacher <edick_at_idcomm.com>
Date: Wed Apr 10 19:15:26 2002

Actually, on most PROMs, a blown fuse yields a 1, since the unprogrammed state
of the fuse is a 0. Moreover, if you stop to think about it, if you have a
fuse and pull it low, it will open the link to ground, hence produce a 1. I
suppose registered PROMs might behave differently, since their polarity can be
inverted. I've also gotten hold of a TI PAL recently, which, unlike all the
MMI and AMD PALs I'm accustomed to using seems to have an inverted fuse array.
This was quite surprising in light of my prior experience with MMI, Signetics,
and AMD.

Dick

----- Original Message -----
From: "Roger Merchberger" <zmerch_at_30below.com>
To: <classiccmp_at_classiccmp.org>
Sent: Wednesday, April 10, 2002 2:54 PM
Subject: RE: TTL computing


> Rumor has it that Fred Cisin (XenoSoft) may have mentioned these words:
> >On Wed, 10 Apr 2002, Christopher Smith wrote:
> >> At one point I considered making an "illustrative project" of building
> >> a pseudo fuse blown PROM out of several inline type fuses -- like are
used
> >> in power supplies, for instance.
> >> It would be possible to illustrate not only electronically, but visually,
> >> the way that the ROM works. :) "The black ones are 0s... ;)" (or is that
> >> a 1?)
>
> AFAICT, burned fuses should be a logic 0... but I've never worked with
> anything less than LSI/MSI, so...
>
<snip>
Received on Wed Apr 10 2002 - 19:15:26 BST